Switch



Sept. 11, 1934. M. .1. JOHNSON SWITCH Filed Oct. 18, 1932 lab HoPatented Sept. 11, 1934 UNITED STATES PATENT OFFICE to The Lewis Enlin Cmpany, Naugatuck, Conn., a corporation of Connecticut ApplicationOctober 18, 1932, Serial No. 638,292

4 Claim.

This invention relates to switches particularly of the type adapted foruse with currents of low voltage.

In certain phases of the electrical arts, as for 5 instance when it isdesired to measure temperatures or other conditions by means ofthermocouples, the contact-resistance is a factor and it is essentialthat it be reduced to a minimum. For instance, in the example mentionedwhere the current source is a thermocouple the contact resistance mustbe substantially nil in order for the instrument properly to indicatethe temperature.

Accordingly it is an object of this invention to provide a switch havingvery low contact resistance.

Again referring to the example given, where the source of current is athermocouple, it is frequently desired to have a single indicatinginstrument which may be connected to one after the other of thethermocouples, and frequently as in the case of airplanes testing to alarge number of points when it is desired to determine the temperature.

' An object of this invention is to provide a rotary switch which willpermit an indicating instrument to be connected to the thermocouples oneafter the other with a minimum of current leakage, both as between theleads coming from the thermocouples and the leads coming from theindicating instrument, and yet permit a large number of thermocouples tobe controlled by the single switch.

A feature of the present invention is the provision of a rotary switchin which the contact arm is given a definite step-by-step movement, sothat there is no danger of the arm engaging two contacts at the sametime which would result in the danger of short-circuiting, or, in givingan improper reading to an indicating device if the switch iselectrically connected for such a purpose.

Another feature of the present invention is the provision of a rotaryswitch structure which may be used equally well as one-way single makeand break switch, or, as a two-way double make and break switch. To thisend, there is provided a main working mechanism which, if used singly,is particularly adapted for series operation and, when used doubly, onesuperposed upon the other, is particularly adapted for two-wayoperation.

It is another object of the present invention to provide a rotary switchespecially adapted for use in quickly and alternatively connecting aplurality of testing devices such as thermocouples with a plurality ofindicating devices in one form, and to provide a related device adaptedto quickly and alternatively connect a plurality of test devices to asingle indicating device by the mere expedient of turning a singleactuator step-by-step into various stations.

A feature of the present invention is the provision of a plurality ofsuperposed thin switch arms with fingers for engaging the contactsrather than a single comparatively heavy arm, which improve electricalconnection between the contacts. In one form, these arms are supportedat a point remote from the switch actuating shaft in such manner that asubstantially equal amount of pressure is applied by the switch arms toboth a main contact near the center of switch and the secondary contactswhich are located a considerable distance from the center.

Another feature of the present invention is the provision of a bearingwhich serves the double purpose of journaling the actuator shaft andforming a main contact.

, A further feature is the provision of a built up switch unit which maybe assembled upon an end cap of the switch casing and quickly assembledto the casing by merely sliding it into place. This unit is alsoarranged to align and support a large number of current conducting 85.wires.

Other features and advantages will appear hereinafter.

In the drawin Figure 1 is a front view of the rotary switch of thepresent invention.

Fig. 2 is a sectional view taken axially through the center of theswitch, on the line 2-2, Fig. 1.

Fig. 3 is a cross-sectional view taken on the line 3-3, Fig. 2.

Fig. 4 is a similar cross-sectional view taken on the line 44, Fig. 2.

Fig. 5 is a cross-sectional view taken on line 5-5, Fig. 2, and showsthe structure for insuring a step-by-step movement.

Fig. 6 shows the switch of the present invention connected in parallelwith a plurality of test devices and a single indicating device.

Fig. 7 is an axial sectional view similar to Fig. 2, but shows theone-way form.

Fig. 8 is a plan view of the one-way form of switch connected with aplurality of test devices and a plurality of indicating devices.

Because the switch of the present invention will find its greatestuse-or application in a twoway form (double make and break) as shown inFigs. 2, 3, 4 and 6 in particular, this form will be described first,although it should be understood that parts thereof are equallyadvantali geous in the one-wayform described hereinafter.

The two-way switch 12 comprises a cylindrical casing 13 having screwreceiving ears 14-for attachment to an instrument board or the like, andis enclosed with a dial plate 15 on the front and with a cap 16 at theback. The dial plate is held upon the casing with small screws 17 andthe cap is held in place with screws 18 passing through the casing andentering suitably threaded holes in an extension 19 portion of the capwhich fits within the casing.

According to the present invention the cap also serves as a mount for alower switch unit 20 and an upper switch unit 21 in that form of theinvention shown in.Figs. 2 to 6 inclusive and for the switch unit 22 inthat form of the invention shown in Figs. 7 and 8.

. The lower switch unit 20 comprises a plate 23 of insulating materialprovided with a hole near the center adapted to receive a bearing 24which may be either forced in place or held in place by a nut 30 drawingthe bearing into the plate until a flange 25 thereon is drawn firmlyinto engagement with the plate. The bearing is provided with a hole 26in which ashaft 27 is supported for rotation.

. The main bearing, in this form of the invention, also serves as a maincontact and for this purpose a lead 28 and a terminal washer 29 areconnected to the shank of the bearing where they are held in place withthe nut 30 when the latter is tightened.

The plate 23 also forms an insulating support for a plurality ofsecondary contacts 31 which are preferably circularly arranged relativeto the axis of the bearing 24 and the shaft 27. These contacts areprovided with a head portion and a shank extending through suitableholes with a nut 32 on the under side to draw and hold them in place.Feed wires 33 are then connected to the individual contacts through themedium of a second nut 32 on each threaded shank, or by spot solderingas shown in Fig. 2. Only one or two representative wires 33 are shownconnected to the contacts 31, but in regular use a wire would beconnected to each contact. This has been done so that other details inthe drawing may be shown more completely- Current is passed from theindividual secondary contacts 31, one at a time, to the main contact 24through a yielding switch arm 34 carried by the shaft 27. Downturnedfingers 35 and 36 on the arm engage with the contacts 24 and 31respectively. In order to insure good electrical connection andtransmission of current the arm 34 is preferably made of several pieces34', (four as shown) superposed upon each other, and with the endfingers 35 and 36 on eachslightly beyond the ends of the next lowerpiece and with succeeding fingers of slightly greater length than thethickness of the material so that each piece is capable of a maximumflexing action and so that each finger is sure to connect with thecontacts.

This connection and flexing action is further improved according to thepresent invention by the provision of a switch arm carrier 37 ofinsulation connected to the shaft with a pin 38 and arranged to supportthe arm pieces 34' at a point remote from the axis of the shaft 27 andnear the center of the arm 34 so that all of the fingers 35 and 36engage the contacts 24 and 31 with substantially equal pressure.Accordingly, the carrier 37 is provided with an abutment 38a oflsetrelative to the axis of the shaft, and a screw 39 is passed through thearms 34' and into a suitable threaded hole to secure thearms to theoflset abutment 38a. on the carrier. Insulation of the arm 34 from theshaft 27 is effected by the carrier 37 which is made of insulation, andby a sleeve 40 of insulation on the shaft 27 which prevents a U shapedportion 41 (see Fig. 3) of the arms from engaging the shaft.

It is customary to provide a single flat switch arm in rotary switches,and when this is provided it is necessary to have it made of thickmaterial. Such an arm does not have much resiliency and consequentlythere is the danger of both insuflicient and excess pressure on thecontacts which would cause, respectively, incomplete electricalconnection and special effort in operating the switch. However, with thepresent invention the several thin arms 34' may be drawn yieldinglytoward the contacts a considerable extent so that there is never anydanger of insuflicient conduction and will yield easily for highcontacts and thereby not impede operation of the switch. Also thedownturned fingers 35 and 36 tend to cut into the top of the contactsand thereby remove corrosion and insure good electrical connection atall times.

The shaft 27 and associated switch arm 34 may be rotatably maintained inthe desired axial position with the desired degree of pressure on thecontacts by passing any suitable collar or a collar 42 portion of anindex plate 45 onto the shaft until it engages with the lower end of thebearing 24 where it is fastened in position on the shaft with a screw 43after the contact arm 34 is located for the proper amount of pressureupon the contacts 24 and 31. Although this type of connection serves tokeep the fingers on the switch; arm in goodengagement with the contactsthere is no snap action from contact to contact, which is desirable insome instances.

In its preferred embodiment the present in= vention provides a structure44 for effecting a snap action between the contacts 31, one after theother, so that there is a quick make and break electrically and adefinite step by step movement of the switch arm, and so that thefingers 36 on the switch arm 34 will engage with only one contact 31 ata time. The present preferred arrangement for accomplishing thiscomprises a combined collar 42, and the index plate 45 connected to thelower end of the shaft 27 with a set screw 46 and having a plurality ofequally spaced and radially arranged indexing notches 47 in which aspring plunger. 48 is adapted to work. The spring plunger comprises asleeve 49 having a threaded connection 50 with the plate 23 and having abore in which a plunger pin 51 is supported for axial movement andyieldingly urged toward the index notches 47 by a spring 52 which isheld in the bore by a screw 53. The index plate is located on the shaftso that the plunger 51 is in one of the notches 47 when the switch arm34 is centered upon a contact 31 so that as a user begins to rotate theshaft 27 the angular walls of the notches 47 tend to restrain rotationuntil the end of the plunger reaches the top of the plate. Thereafter, aquick snap action of the plate 45 and switch arm 34 to the nextsucceeding sta- 1193 is accomplished as the end of the plunger ridesover one of the intermediate flats 54 between thenotches. The plunger 51snaps into the next succeeding notch so that there is a positivestep-by-step action, and a quick make and break electrical connectionbetween the contacts. I

The upper switch unit 21 is similar to the lower switch unit 20 in manyrespects, for it comprises a plate 23', hearing and main contact 24 anda plurality of secondary contacts 31'. However, another lead 55 isconnected to the main contact and a plurality of other leads 56 areconnected to the secondary contacts. Also, a slightly longer shaft 27ais Journaled in the bearing. A small carrier 57 is connected to thisshaft with a pin 58 and like the carrier 37 it supports an arm 34apreferably made from a plurality of arm pieces on an abutment 59 with ascrew 39 offset from the axis of the shaft so that fingers 35' and 36thereon engage the contacts 31' and 24' with substantially equalpressure.

The switch arms 34a on the upper switch unit 21 are like the arms 34 onthe lower switch unit 20 insulated from the shaft 27a by the carrierblock 57 which is made of insulating material and engagement of the armswith the shaft is prevented by a sleeve 40 of insulating material. Afterthe contact arms are assembled to the carrier 57 the shaft 27a is passedthrough the bearing 24 and moved toward the contacts until fingers 35'and 36' engage their respective contacts with the desired degree ofpressure where they are held in place by a space sleeve 60 engaging'thebottom of the bearing 24' when a clutch collar 61 is fastened on theshaft with a screw 62.

The lower and upper switch units 20 and 21 are supported one upon theother and supported on the end cap 16 for rigidity and to preventturning. This assembly is effected by passing the main lead wires 28 and55' through suitable apertures 63 and 64 in the plate 23 and apertures65 and 66 in the cap 16; and by passing the secondary lead wires 56 ofthe upper switch unit 21 through apertures 67 in the plate 23 of thelower switch unit and through apertures 68 of the end cap while thesecondary leads 33 of the lower switch unit 20 are passed through a setof apertures 69 in the end cap. If preferred, the wire clearancepassages 63, 64 and 67 may, in order to facilitate assembly, be in theform of notches on the periphery such as the one or two representativenotches 70 shdwn in Fig. 3. However, location and rigidity of the leadsis better insured by threading them through the holes as describedhereinbefore.

After the leads are so threaded through their respective apertures theupper and lower switch units 20 and 21 are connected through the mediumof a clutch connection 71 comprising a plurality of pins 72 on thecollar 61 extending into suitable holes 73 provided therefor in thecarrier 37 of the lower switch unit. This clutch connection insuresconjoint rotation of the shafts 27 and 270.. A substantially close fitis provided by this clutch so that the spring plunger 51 and indexingdevices 44 of the lower switch unit ,effects a conjoint snap movementand quick make and break electrical action of the upper switch unit 21.

The dial plate 15 may be fastened in place with the screws 17 eitherbefore or after the switch units 20 and 21 and end cap 16 are connectedto the casing for the upper end of the shaft 27a passes through a hole72 therein, after which an insulating sleeve 73v is placed on the shaftso that there will be no short circuit between the plate and the shaftand then a handle or actuator knob 74 is passed onto a reduced sectionof the shaft where it is held in place with a holding screw 75. Apointer 76 is connected to the actuator knob which points in thedirection of the station numerals 77.

A plurality of standards 80 are connected to the plate 23' of the upperswitch unit with screws 81 to properly space and support the upper unitrelative to the lower unit, and completed by a threaded shank portion 82of lower standards 83 passing through the plate 23 of the lower switchunit to enter threaded holes 84. Connection of the two united switchunits to the end cap 16 is then accomplished by passing flat head screws85 through the end cap and tightening them in the threaded holes 86 ofthe lower standards 83. This structure is such that all of the assemblywork may be done extraneously of the case 13, may be added to the caseeasily in final assembly,'and may be taken from the case veryconveniently for repairing or alteration in the wiring.

This duplex form of switch 12 is especially advantageous where it isdesired to have a two way or double make and break switch action and isespecially advantageous for use in connecting a plurality of thethermocouples 78 or other similar test devices to a single indicatingdevice 79 as shown schematically in Fig. 6. The indicating device hasthe two leads 28 and 55 extending to the main contacts 24 and 24'respectively and each thermocouple 78 has the wires 33 and 56 extendingto the secondary contacts 31 and 31' on the lower and upper switch units20 and 21 respectively. This arrangement is such that current from athermocouple 78 passes through the leads 33 and 56 to associatedsecondary contacts 31 and 31' on the lower and upper switch units,thence through switch arms 34 and 34a to main contacts 24 and 24 andthereafter through the leads 28 and 55 to the indicating device 79, fora reading. As the knob 74 and associated switch arms are moved intosuccessive stations individual thermocouples 78 are connectedelectrically to the one indicating device.

From the above it will be seen that the present invention provides aswitch for the wire of each pair of leads from the thermocouples whichare connected respectively to contacts on widely separated insulatedplates and that the leads from the indicating instrument are alsorespectively connected to contacts on these widely separated plates.Hence when the switch handle 74 is turned an individual pair of leadsfrom a single thermocouple and no other leads from any thermocouple isconnected to the pair of leads from the indicating instrument. In thisway the use of common return wires or other expedients heretoforeemployed and their disadvantages are avoided.

In Fig. 7 there is shown a modified form of the present inventionembracing many of the novel features already described in detail in aone-way or series operation switch 22 which is capable of only a singlemake and break in the electrical circuit. This form of switch like thelower and upper switch units 20 and 21 comprises the plate 23 supportinga plurality of alternate contacts 31a. and 31b and a bearing 24 for ashaft 87 near the center. In this form.

of the invention the bearing is notutilized as a.

main contact and may for economy be dispensed with by journalling theshaft directly in the insulating plate 23; however, to reduce wear andto improve operation of the switch it is deemed desirable now to providethe metal bearing.

In this form, however, the shaft 87 supports a carrier 88 of insulation,which extends a substantially equal amount on both sides of the shaft toprovide a double support for a switch arm 89. The latter in itspreferred form extends in substantially a straight line across the axisof the shaft 87 and at its outer ends is provided with turned down'fingers 90 and 91. The arm at its center is provided with a holesufficiently large to clear the shaft at all times and is connected toboth sides of the carrier with screws 92. This arm 88 similarly to thearm 34 in Figs. 2, 3, and 4 is preferably made of a plurality of thinarm pieces 89 each superposed arm piece being slightly longer andintegral fingers of each being of greater height than the next lowerone. Thus, each of the arm pieces is capable of individual flexing andthe fingers on each are capable of fully' engaging the contacts.

The switch arm may be yieldingly held in engagement with the contacts31a and 311) by moving them toward the contacts until the desired degreeof pressure is obtained and then tightening the collar 42 to the lowerend of the shaft with the set screw 43. It is preferred, however, toalso use the index plate 45 and the spring plunger 48 in the plate 23 at50 so that a snap movement and a quick make and break action occurs. Thecarrier 88 and switch arms thereon are connected to the shaft with a pin93 so that they cannot shift vertically and to insure their rotationwith the shaft.

This form of the present invention is especially adapted for the use inelectrically closing a plurality of lines 94, each line including athermocouple 95 and an associated indicating device 96, with a wire 97extending from one pole of the thermocouple directly to the indicatingdevice, another wire 98 extending from the indicating device to thecontact 31a on the 'switch, while yet another wire 99 extends from theother pole of the thermocouple to an associated contact 31b on theswitch. Thus, it will be seen that with this form of switch thecircularly arranged contacts contain sets of associated input and outputcontacts 31a and 31b which are preferably diagonally opposite each otheracross the axis of the shaft 87, and that fastened to the end cap withflat head screws 102. This assembly is then placed within a short casing103 and held in place with screws 18. A dial plate 150. is connected tothe casing with screws 17. In this form, however, the

switch is provided with only half as many working stations if the plate23 with twenty eight contacts 31a and-31b is used. For example,

if the ends and 91 of the switch arm 89 are diagonally opposite,- theend 91 will engage with the contact underlying the numeral 28 Fig. 1when the end 90 movesin a clockwise direction to a contact underlyingthe numeral 14. Thus, the dial 15a in this form contains the run ofnumerals 1 to 14 only. Assembly is completed by moving an insulatingsleeve 104 onto the shaft 87 and connecting a handle or actuator knob 74to the shaft in the same manner as shown in Fig. 2.

Variations and modifications may be made within the scope of thisinvention and portions of the improvements may be used without others.

Having thus described the invention, what is claimed as new and forwhich it is desired to obtain Letters Patent, is:-

1. In a rotary switch, a metallic enclosing casing; a stationary plateof insulation in said casing and secured thereto; a metal bearing insaid plate and forming a main contact; a shaft extending into saidcasing and journaled in said bearing; a plurality of secondary contactson said plate; a switch arm adapted to engage with and pass current fromsaid main bearing contact to said secondary contacts; a handle andpointer on the shaft exteriorly of the casing; and an arm on said shaftwithin the easing adapted to support the switch arm at a point remotefrom the'axis of the shaft and substantially midway the length of theswitch arm, so that the switch arm engages the main contact andsecondary contacts with equal pressure, the switch arm being bifurcatedto straddle the shaft and engage the opposite portion of the maincontact.

2. In a rotary switch, the combination of a plate of insulation carryinga main contact and secondary contacts and having a shaft journaled insaid plate carrying a switch arm adapted to bridge the gap between saidmain contact and said secondary contact; another plate of insulationcarrying a main contact and secondary contacts and having a shaftjournaled therein carrying a switch arm adapted to bridge the gapbetween said main contact and said secondary contacts; means forsupporting one of said plates upon the other and in spaced parallelrelation; and a connection joining the shaft in the one plate with theshaft of the other plate for conjoint rotation, said connectionpermitting longitudinal shifting of one shaft relative to the other andincluding a nonmetallic member to insulate one shaft from the other.

3. In a rotary switch, the combination of a plate of insulation carryinga main contact and secondary contacts and having a shaft journaled insaid plate carrying a switch arm adapted to bridge the gap between saidmain contact and said secondary contact; another plate of insulationcarrying a main contact and secondary contacts and having a shaftjournaled therein carrying a switch arm adapted to bridge the gapbetween said main contact and said secondary contacts; means forsupporting one of said plates upon the other and in spaced parallelrelation; and a connection joining the shaft in the one plate with theshaft of the other plate for conjoint rotation, said connectionpermitting longitudinal shifting of one shaft relative to the other andincluding a nonmetallic member to insulate one shaft from the other, oneof said shafts having an operating handle and the other having a detentplate :01- holding the shafts in predetermined adable with the latterand the back plate of the casing; main .and secondary contacts and aswitch arm carried by said second-named insulating plate; and guideapertures in said firstnamed plate of insulation through which leadwires extending through the back plate of the casing to the secondarycontacts on the secondnamed plate of insulation may pass and be held inspaced relation and out of engagement with the secondary contacts on thefirst-named plate of insulation.

MANFRED J. JOHNSON.

III

